Local area network of serial intelligent cells

ABSTRACT

A serial intelligent cell (SIC) and a connection topology for local area networks using Electrically-conducting media. A local area network can be configured from a plurality of SIC&#39;s interconnected so that all communications between two adjacent SIC&#39;s is both point-to-point and bidirectional. Each SIC can be connected to one or more other SIC&#39;s to allow redundant communication paths. Communications in different areas of a SIC network are independent of one another, so that, unlike current bus topology and star topology, there is no fundamental limit on the size or extent of a SIC network. Each SIC can optionally be connected to one or more data terminals, computers, telephones, sensors, actuators, etc., to facilitate interconnectivity among such devices. Networks according to the present invention can be configured for a variety of applications, including a local telephone system, remote computer bus extender, multiplexers, PABX/PBX functionality, security systems, and local broadcasting services. The network can use dedicated wiring, as well as existing wiring as the in-house telephone or electrical wiring.

This is a continuation of copending parent application Ser. No.11/264,011 filed Nov. 2, 2005, itself a continuation of grandparent Ser.No. 10/178,223, filed Jun. 25, 2002, which itself is a continuation ofgreat-grandparent U.S. patent application Ser. No. 09/123,486 filed Jul.28, 1998, now U.S. Pat. No. 6,480,510, issued Nov. 12, 2002.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to local area networks and, moreparticularly, to local area network topologies based on serialintelligent cells.

Bus Topology

Most prior art local area networks (LAN) use a bus topology as shown byexample in FIG. 1. A communication medium 102 is based on two conductors(usually twisted pair or coaxial cable), to which data terminalequipment (DTE) units 104, 106, 108, 110, and 112 are connected, viarespective network adapters 114, 116, 118, 120, and 122. A networkadapter can be stand-alone or housed within the respective DTE.

This prior art bus topology suffers from the following drawbacks:

1. From the point of view of data communication, the medium can varysignificantly from one installation to another, and hence properadaptation to the medium cannot always be obtained.

2. The bus topology is not optimal for communication, and hence:

a) the maximum length of the medium is limited;

b the maximum number of units which may be connected to the bus islimited;

c) complex circuitry is involved in the transceiver in the networkadapter;

d) the data rate is limited.

3. Terminators are usually required at the ends of the medium, thuscomplicating the installation.

4. Only one DTE can transmit at any given time on the bus, and all otherare restricted to be listeners.

5. Complex arbitration techniques are needed to determine which DTE isable to transmit on the bus.

6. In case of short circuit in the bus, the whole bus malfunctions, andit is hard to locate the short circuit.

7. Addresses should be associated independently with any networkadapter, and this is difficult to attain with bus topology.

Star Topology

A number of prior art network devices and interconnections summarizedbelow utilize star topology.

The multiplexer is a common item of equipment used in communication,both for local area networks and wide-area networks (WAN's). It is usedin order to provide access to a data communications backbone, or inorder to allow sharing of bandwidth between multiple stations. As shownin FIG. 2, one side of a multiplexer 202 is usually connected to asingle high data rate connection 204 (“highway”), but several suchconnections can also be used. The other side of multiplexer 202 hasmultiple low data rate connections 206, 208, 210, 212, and 214. Theellipsis . . . indicates that additional connections can be made. Eachlow data rate connection uses part of the bandwidth offered by the highdata rate connection. These low data rate connections can be of the sametype or different types, and can have different or identical data rates.The multiplexing technique most commonly used is time-domainmultiplexing (TDM). However, frequency-domain multiplexing (FDM) is alsoused.

A popular multiplexer in use is the voice multiplexer, shown in FIG. 3.A pulse-code modulation (PCM) bus 304 handling 2.048 megabits persecond, containing 30 channels of 64 kilobits per second is connected toone side of a PABX/PBX 302, and up to 30 telephone interfaces 308, 312,and 316 are connected to the other side via connections 306, 310, and314. The ellipsis . . . indicates that additional connections can bemade. In this configuration, each channel in the PCM bus can be switchedor be permanently dedicated to a specific telephone line. An example ofsuch system is disclosed in U.S. Pat. No. 3,924,077 to Blakeslee.

Similarly a small private branch exchange (PABX/PBX), as shown in FIG.4, is widely used (usually in an office or business environment) whereseveral outside lines 403, 404, and 405 are connected to one side of aPABX/PBX 402, and multiple telephones 408, 412, and 416 are connected tothe other side via lines 406, 410, and 414, respectively. The ellipsis .. . indicates that additional connections can be made. The PABX/PBXconnects an outside line to a requesting or requested telephone, andallows connection between telephones in the premises.

In the configurations described above, star topology is used in order toconnect to the units to the multiplexer, which functions as the networkhub. The disadvantages of star topology include the following:

1. A connection between each unit and the network hub is required, andthe wiring required for this connection can involve a lengthy run.

Thus, when adding new unit, an additional, possibly lengthy, connectionbetween the new unit and the network hub must be added.

2. No fault protection is provided: Any short circuit or open circuitwill disrupt service to the affected units.

3. The multiplexer can impose extensive space and power requirements.

Computer Interfaces

Various interface standards have been established in order to allowinteroperability between the PC (personal computer) or workstation andits various connected elements. These standards usually relate to bothmechanical and electrical interfaces, and include industry standardarchitecture (ISA), extended industry standard architecture (EISA),Personal Computer Memory Card Industry Association (PCMCIA), intelligentdrive electronics (IDE), small computer system interface (SCSI), andothers. Each added hardware unit usually utilizes a specific softwaredriver for interoperability with the specific platform. These protocolsare applicable to small distances only, and allow units to be housedwithin or nearby the PC or workstation enclosures. For example,equipping a PC for video capture could involve a plug-in ISA card housedwithin the PC on the motherboard, a video camera connected to the card,and a software driver. This configuration does not allow remote videomonitoring.

Relevant Prior Art

The use of the same wire pair or pairs for both power and datacommunication is well known, and is widely used in telecommunications,from “Plain Old Telephone Service” (“POTS”) to Integrated ServicesDigital Network (ISDN) and broadband services in the local-loopincluding other Digital Subscriber Line (xDSL) technologies. Such aconcept is described, for example, in U.S. Pat. No. 4,825,349 to Marcel,describing using two pairs for such a scheme. A DC-to-DC converter forsuch DC feeding is described, for example, in U.S. Pat. No. 4,507,721 toYamano et al.

The concept of power line communication (PLC) is also widely known.However, in most cases the connection is similar to a LAN environment,in which a single transmitter occupies the entire medium. Examples ofsuch techniques include X-10 and the consumer electronics bus (CEBus,described in the EIA-600 standard). Much of this technology uses complexspread-spectrum techniques in order to accommodate problematic media(characterized by high amounts of noise and interference). Even withsuch improved technologies, however, the data rate obtained isrelatively low.

Prior art in this field includes U.S. Pat. No. 5,684,826 to Ratner, U.S.Pat. No. 5,491,463 to Sargeant et al., U.S. Pat. No. 5,504,454 toDaggett et al., U.S. Pat. No. 5,351,272 to Abraham, U.S. Pat. No.5,404,127 to Lee et al., U.S. Pat. No. 5,065,133 to Howard, U.S. Pat.No. 5,581,801 to Spriester et al., U.S. Pat. No. 4,772,870 to Reyes, andU.S. Pat. No. 4,782,322 to Lechner et al. Other patents can be found inU.S. Class 340/310 (sub-classes A/R and others) and International ClassH04M 11/04.

The concept of using existing telephone wiring also for datacommunication is first disclosed in U.S. Pat. No. 5,010,399 to Goodmanet al., where video signals superimposed over the telephone signals areused. However, the scheme used is of the bus type and has the drawbacksof that topology. Similarly, the idea of data transmission over a publicswitched telephone network (PSTN) using the higher frequency band iswidely used in the xDSL systems, as is disclosed in U.S. Pat. No.5,247,347 to Litteral et al. The patent discloses an asymmetric digitalsubscriber line (ADSL) system. However, only a single point-to-pointtransmission is described over the local-loop, and existing in-housewiring is not discussed, and thus this prior art does not disclose howto configure a full multipoint network. Multiplexing xDSL data and thePOTS/ISDN data uses FDM principles, based on the fact that the POTS/ISDNservices occupy the lower portion of the spectrum, allowing for the xDSLsystem to use the higher bandwidth.

A home bus network using dedicated wiring is disclosed in U.S. Pat. No.4,896,349 to Kubo et al, and a home automation network based on a powerline controller (PLC) is disclosed in U.S. Pat. No. 5,579,221 to Mun.U.S. Pat. No. 4,714,912 to Roberts et al is the first to suggestcommunicating data over power lines not in bus topology but as‘break-and-insert’. However, only single conductor is used, and thereceivers are all connected again using a bus topology.

In addition, U.S. patent application Ser. No. 08/734,921, Israel PatentApplication No. 119454, and PCT Patent Application No. PCT/IL97/00195 ofthe present inventor disclose a distributed serial control system ofline-powered modules in a network topology for sensing and control.These documents, however, do not disclose a local area network for datacommunications.

The prior art documents mentioned above are representative examples inthe field. Certain applications are covered by more than one issuedpatent.

There is thus a widely recognized need for, and it would be highlyadvantageous to have, a means of implementing a local area network fordata communications which does not suffer from the limitations inherentin the current methods. This goal is met by the present invention.

SUMMARY OF THE INVENTION

The present invention is of a local area network for data communication,sensing, and control based on serially connected modules referred to as“serial intelligent cells” (SIC's). An example of a local area networkof such devices according to the present invention is illustrated inFIG. 7, to which reference is now briefly made. In this example, SIC's700, 702, 704, 706, and 708 are connected by one or more conducting wirepairs (such as a twisted pair 710). This allows chaining, such as SIC700 to SIC 702 to SIC 704. However, SIC 700, SIC 706, and SIC 708,located at the ends are equipped with single connection. SIC 704 isequipped with three connections, and even more connections are possible.A SIC may be interfaced to one or more DTE's, as illustrated by a DTE714 interfaced to SIC 700 and by DTE's 716 and 718 interfaced to SIC704. SIC's need not have an interface, however, as is illustrated by SIC706 and SIC 702. SIC 702, though, serves as a repeater, connecting SIC700 and SIC 704. It is to be noted that the networks according to thepresent invention utilize electrically-conducting media to interconnectthe SIC's. Each electrically-conducting medium connects exactly twoSIC's into a communicating pair of SIC's which communicatebidirectionally and independently of other communicating pairs in thelocal area network. Electrically-conducting media are media whichtransmit signals by conducting electrical current or by propagatingelectrical potential from one point to another. Electrically-conductingmedia include, but are not limited to wires, twisted pair, and coaxialcable. But electrically-conducting media do not include media such asfiber optic lines, waveguides, microwave, radio, and infraredcommunication media.

As noted above, SIC's in a communicating pair communicatebidirectionally. For example, SIC 704 can initiate communication (as asender) to SIC 702 (as a receiver), but SIC 704 can just as wellinitiate simultaneous communication (as a sender) to SIC 700 (as areceiver). Bidirectional communication can take place simultaneously,and herein is taken to be equivalent to “full duplex” communication. Inaddition, as noted above, the communication between the SIC's of acommunicating pair is independent of the communication between the SIC'sof any other communicating pair, in that these communications neitherpreclude nor affect one another in any way. Furthermore, everycommunication between SIC's is a “point-to-point communication”, whichterm herein denotes a communication that takes place between exactly onesender and exactly one receiver. This is in contrast to a bus-basedcommunication, in which there are many (potential) receivers and many(potential) senders. Consequently, in the topology according to thepresent invention, there is automatically a termination in the physicallayer at each end of a connection (a SIC), both simplifying theinstallation and insuring more reliable communication.

The topology according to the present invention is superior to the priorart bus topology in the following ways:

1. There is no physical limit to the number of SIC's which may beinstalled in the network, and hence no physical limit to the number ofDTE's in the network.

2. Point-to-point communication allows higher data rates over greaterdistances.

3. Point-to-point communication requires less complex circuitry than buscircuitry.

4. Several SIC's can transmit and receive simultaneously. For example,SIC 700 can communicate with SIC 702 while SIC 704 communicatessimultaneously with SIC 706.

5. There is no need for arbitration, allowing more efficient utilizationof the network. Furthermore, priorities can be assigned to each SIC or,alternatively, to each specific message to allow the data routing totake care of priorities.

6. Addresses may be assigned by the network

7. In the case of failure of any conductor or SIC, the network can sensethe fault immediately, and the specific location of the fault (up to thespecific SIC pair) is easily obtained.

Therefore, according to the present invention there is provided a localarea network for data communication, sensing, and control including aplurality of serial intelligent cells interconnected exclusively byelectrically-conducting media into at least one communicating pair,wherein: (a) each of the electrically-conducting media interconnects nomore than two of the serial intelligent cells; (b) each of thecommunicating pair includes one of the electrically-conducting media andexactly two of the serial intelligent cells; (c) each of thecommunicating pair engages in a communication exclusively over theelectrically-conducting media; and (d) each of the communicating pairengages in the communication bidirectionally and independently of thecommunication of any other of the communicating pair.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 shows a common prior art LAN bus topology

FIG. 2 shows a typical prior art multiplexer.

FIG. 3 shows a prior art voice multiplexer (star topology).

FIG. 4 shows a prior art voice exchange configuration (star topology).

FIG. 5 is a block diagram of a SIC for control applications according tothe present invention.

FIG. 6 is a block diagram of a SIC for data communications according tothe present invention.

FIG. 7 shows a LAN topology utilizing the devices of the presentinvention.

FIG. 8 shows an alternative LAN topology utilizing the devices of thepresent invention.

FIG. 9 shows a SIC-based multiplexer—PABX/PBX according to the presentinvention.

FIG. 10 shows a local area network according to the present inventionused as a computer bus extender.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principles and operation of a local area network according to thepresent invention may be better understood with reference to thedrawings and the accompanying description.

FIG. 5 is a block diagram of a representative SIC 500 for use in controlapplications. A first line interface 502 is a first port for connectingto the previous SIC to receive incoming electrical power and local areanetwork data over electrically-conducting medium 503, which mayoptionally be connected to an electrical power main 501, so that SIC 500may be powered from electrical power main 501. Line interface 502 mayinclude the connector, fuse, lightning arrester and other protectionsuch as noise filters, etc. The incoming power/data signal is fed to afirst power/data splitter/combiner 504, which de-couples the (highfrequency alternating current) data signal from the power. Such apower/data splitter/combiner 504 (denoted for brevity in FIG. 5 as “P/Ds/c”) can be implemented by methods well-known in the art, such as usinga center-tap transformer, or alternatively with active components. Thedata signal is fed to a first modem 506 allowing bidirectionalcommunication, while the power is fed to a power supply 520. The abovescheme assumes that both power and data are carried by the same networkwires (line-powering). FIG. 5 illustrates the case where the SIC isline-powered by alternating current (for example, by the electricalpower main), in which case power/data splitter/combiner 504 is an ACpower/data splitter/combiner, which separates a low-frequencyalternating current power from the higher-frequency data signal.Otherwise, in the case where the SIC is line-powered by direct current,power/data splitter/combiner 504 is a DC power/data splitter/combiner,which separates direct current power from the data signal. In some casesthe line-powering method is not used. For example, power can be carriedby dedicated lines routed in conjunction with the data wiring.Alternatively, the SIC can be locally powered by a local power-supply.In both cases, the power/data splitter/combiner is not required, and thepower lines are directly connected to the SIC power-supply, while thedata connects directly to the modems. Parts of the SIC are shownoptionally housed within an electrical outlet 524, such that connectionsto the local area network as well as to the electrical power mains maybe made from electrical outlet 524. Electrical power from electricaloutlet 524 can be fed to an optional electrical appliance 525. Inaddition, SIC 500 contains an optional electrical power main feed 505which can also power electrical appliances or other devices.

Power-supply 520 provides the required voltages for the SIC and payloadoperation, and also outputs the power to a second Power/datasplitter/combiner 510, for coupling to the next SIC. Communication withthe next (fed) SIC is performed via a second modem 512 connected to asecond line interface 514 via power/data splitter/combiner 510, similarto power/data splitter/combiner 504 as previously described. Lineinterface 514 feeds to electrically-conducting medium 515, whichconnects to the next SIC. Modems 506 and 512 can be standard RS-485,RS-232, or any simple similar data interface transceiver. Alternatively,a complex transceiver can be used for achieving long ranges orhigh-speed operation. CPU and firmware contained in a control block 522control and monitor the unit operation and communication, as well ascontrol the payload through a payload interface 508 interfacing with apayload illustrated by a sensor/actuator 509. For example, interface 508can implement a 4-20 ma standard interface. In a similar way, SIC 500can be used for communication over the power line. To do this, payloadinterface 508 is replaced by a communication port and sensor/actuator509 will be replaced by a DTE.

A SIC for use in data communications as shown in FIG. 6 is substantiallysimilar to that used in control applications as shown in FIG. 5, but hassome specific differences as noted. Also illustrated in FIG. 6 is thecase where the local area network data is carried overelectrically-conducting media which are part of the telephone wiring ofa building. A SIC 600 has a first line interface 602 as a first port forconnecting to the previous SIC to receive incoming power, local areanetwork data, and telephony data via an electrically-conducting medium603. Line interface 602 may include the connector, fuse, lightningarrester and other protection such as noise filters, etc. The incomingpower/telephony/data signal is fed to a first telephony/datasplitter/combiner 604 (denoted for brevity in FIG. 6 as “T/D s/c”),which de-couples the local area network data from the power andtelephony data. Such a telephony/data splitter/combiner 604 can beimplemented by methods well-known in the art, such as using ahigh-pass/low pass filter, or alternatively with active components. Thelocal area network data signal is fed to a first modem 606 allowingbidirectional communication, while the power (DC) is fed to a powersupply 620, and the telephony data is fed to power/telephone interface624.

Power-supply 620 provides the required voltages for the SIC and payloadoperation, and also outputs the power to a second telephony/datasplitter/combiner 610, for coupling to the next SIC. Communication withthe next (fed) SIC is performed via a second modem 612 connected to asecond line interface 614 via telephony/data splitter/combiner 610,similar to telephony/data splitter/combiner 604 as previously described.Line interface 614 connects to an electrically-conducting medium 615,which connects to the next SIC. Modems 606 and 612 can be standardRS-485, RS-232 or any simple similar data interface transceiver.Alternatively, a complex transceiver can be used for achieving longranges or high-speed operation. CPU and firmware contained in a controlblock 622 control and monitor the unit operation and communication, aswell as control the payload through a payload interface 608 interfacingwith a payload 609, which may include sensors and actuators. Forexample, interface 608 can implement a 4-20 ma standard interface. SIC600 also includes an optional power/telephone interface 624, containedfor example in a telephone outlet 625, as well as one or morecommunications interfaces, such as a communication interface 626connected to a DTE 628.

In the case of DC line feeding, the power supply may be equipped with aline reversal function (for example, a diode-based bridge) in order toaccommodate a possible wire reversal.

Note that a SIC can be implemented as single device with all componentparts contained within one enclosure, but does not necessarily have tobe so implemented. In the case of a SIC used for data communications orcontrol applications, the hardware may be optionally divided between theSIC module and the DTE/Payload units. In the case of a SIC used fortelephone applications, the hardware may optionally be divided betweenthe SIC, the DTE payload unit, and the telephone outlet, such astelephone outlet 625, which allows connections to both telephoneservices (such as through a telephone 623) and the local area network(such through DTE 628). Telephone outlet 625 may be a wall outlet orjack. All or part of the SIC may be housed within a telephone outletsuch as telephone outlet 625, if desired. Furthermore, for SIC's usedonly as repeaters, a payload interface is not necessary.

Power/data splitter/combiner 510 (FIG. 5) can use various techniquesknown in the art. Coupling can be implemented, for example, as disclosedin U.S. Pat. No. 4,745,391 to Gajjar. Power-supply 520 (FIG. 5) can beconnected to the network using dedicated adapter or via specific SIC.The payload can also be connected using standard Ethernet or other LANinterface, hence emulating the network using the SIC's. Thisconfiguration makes use of standard interfaces, but operates at higherthroughput and data-rates than a conventional LAN.

SIC Addressing

A SIC can include an address. Addresses of SIC's on the network can beassigned via automatic assignment by the local area network itself byalgorithms known in the art, for example as disclosed in U.S. Pat. No.5,535,336 to Smith et al. Addresses can also be assigned via manualassignment, such as by the setting of mechanical switches on the SICunit. Addresses can also be determined by the DTE connected to the SIC,either by means of higher layers as done in most LAN systems, orphysically be means of the connection to the SIC (such as by addresslines).

SIC Powering

A SIC can receive electrical power locally, via a power source locatednear the SIC. However, one power source may be used to power some or allthe SIC's in the local area network using dedicated power lines. Theselines can be routed with the data communication wires. Alternatively,the same electrically-conducting media (the data communication wires)can be used to carry both electrical power and local area network datato the SIC's, by means of techniques well-known in the art, for exampleas in telephone systems. In such a case, a unit is required for couplingthe power supply to the local area network. This can make use of a SIC(such as SIC 706 in FIG. 7) or in a specific dedicated module. Sinceelectrical power is typically distributed at low frequencies (e.g., 60Hertz), whereas local area network data is typically at a much higherfrequency, electrical power can be combined with local area network datausing frequency-domain multiplexing. A SIC can therefore be powered fromthe electrical power mains, and can also deliver electrical power, asillustrated in FIG. 5 and detailed herein above.

The DTE's, sensors, and actuators connected to the SIC's can also belocally powered from the SIC's, or can use the same power resources viathe same channels as the SIC's. Part or all of a SIC can be housedwithin an electrical outlet so that the electrical outlet allowsconnection to the local area network as well as to electrical power.

Control

Although mainly intended to be used as communication network, the systemaccording to the present invention can also be used as a platform toimplement a sensing, control, and automation system. This is achieved byadding to one or more of the SIC's interfaces to sensors or actuators.The signals received by the sensors are transmitted over the network vialogic contained in the SIC's or in the DTE's, which thereupon operatethe relevant actuators. This automation function can be monitored by oneor more of the DTE's.

The operation of the control may be associated with data communicatedover the network (for example, sensing the availability of power to aDTE) or may be independent of it, to allow control decisions to be madelocally.

DTE Interface

The DTE interface can be a proprietary interface or any standard serialor parallel interface, such as ITU-T V.35, ITU-T V.24, etc. In addition,a telephone interface (POTS) or ISDN may be used. This can suit intercomor PBX applications.

Fault Protection

The SIC topology described above can be modified to allow for singlefailure correction. In such a case, the SIC's are connected in a networkwith redundant paths, such as a circular topology as shown in FIG. 8. Inthis example, a SIC 800 is connected to a SIC 802, which is in turnconnected to a SIC 804, which is in turn connected to a SIC 806, whichis in turn connected to SIC 800. When connected in such configuration,any single failure in any conductor, such as in conductor pair 810, willnot effect the system operation, as data routing from any SIC to anyother SIC can be achieved via an alternate path. The term “circulartopology” herein denotes the topology of any local area network of SIC'saccording to the present invention which contains at least twocommunication paths between two different SIC's. For example, in FIG. 8,there are two communication paths from SIC 800 to SIC 804: onecommunication path is from SIC 800 to SIC 802 to SIC 804, and the otherpath is from SIC 800 to SIC 806 to SIC 804. Circular topology providesredundant communication paths that increase the immunity of the localarea network to communication faults. It should be noted that thecircular topology according to the present invention, as shown in FIG.8, differs significantly from the well-known “Token Ring topology” ofthe prior art, as discussed following.

Although circular topology as defined herein can be superficiallysimilar to the Token Ring topology, there are major differences betweenthem. One difference is in the data framing. The Token Ring uses thesame frame structure throughout all communication links in the network,and this requires that the same framing must be recognized by all thecells in the network. In the SIC network according to the presentinvention, however, each communication link (between any two connectedSIC's) is totally independent from all other network communication.Hence, a first SIC can communicate with a second SIC using one type offrame structure and protocol, while the same first SIC can communicatewith a third SIC using a different type of frame structure and protocol

In addition, in a Token Ring network, there is single direction of dataflow at any given time from a single transmitter to one or morereceivers, and usually, the direction of data flow is constant. The SICnetwork according to the present invention, however, does not impose anylimitation on the data flow in any of the communication links. Fullduplex, half duplex or unidirectional communication is possible, and caneven vary from link to link throughout the network. This allows the SICnetwork to support two independent communication routes simultaneously,provided different segments are used. In FIG. 8, for example, SIC 800can communicate with SIC 802 while SIC 804 simultaneously communicatesdifferent data with SIC 806. This capability is not supported by any ofthe other network configurations.

The above differences affect, for example, the vulnerability of therespective networks to faults. In case of single break or short-circuitanywhere in the medium, the Token Ring network will collapse, disablingany further communication in the system. As another example, in thenetwork disclosed in U.S. Pat. No. 4,918,690 to Markkula et al(hereinafter referred to as “Markkula”), this fault affects the physicallayer by disabling the media's signal-carrying capability. The TokenRing network will not function at all since the data layer functionalitybased on unidirectional transmission will not be supported. In contrast,however, a SIC network according to the present invention, will continueto function fully, except for the specific faulty link itself. All otherlinks continue to function normally. Furthermore, the ability tolocalize the fault is not easily performed either in a Token Ringnetwork or in the Markkula network. In the SIC network according to thepresent invention, however, it is simple and straightforward to tracethe fault to the affected link.

Data Distribution over Electrical Power Lines

An important configuration for a network according to the presentinvention uses the electrical power wiring of a building as acommunication media. This can be used, for example, to implement aninexpensive ‘home LAN’. Typical house mains have a connection to singlefeeder with numerous distribution points and outlets. The principlesaccording to the present invention specify a SIC to be located withineach outlet and at each distribution point. This will allow SIC-basedcommunications network, where communication takes place between eachpair of SIC's connected via the wiring. In such a case it is alsoexpected that the mains will also be used to power the SIC's. Aside fromusing the same wiring media, the electrical distribution and thecommunication system sharing the same mains can be totally decoupled.

Another configuration involves adding the SIC to the Mains wiring atpoints distinguished from the mains outlets. The preferred embodiment,however, consists of using the outlets points for both the electricalsupply and the DTE connection points. This involves replacing allelectrical outlets and distribution points with ‘smart’ outlets, havingboth electrical connections and a communications jack. In addition, suchunit may include visual indicators (e.g. LED's) to show thecommunication status, and may also include switches or other means todetermine the outlet address. Such a communication system could be usedfor applications associated with power distribution, as for example tocontrol the load connected to a specific outlet, for remote on/offoperation of appliances, timing of operations, delayed start,disconnection after pre-set time period, and so forth. Such acommunication system could also be used to monitor the power consumed byspecific outlets, such as for Demand Side Management (DSM) or AutomaticMeter Reading (AMR), allowing remote meter reading

The above described topology may also apply to existing wiring. Onecommon example may be power wiring to consumers located in differentlocations. Such wiring typically relies on bus topology with taps. Inorder to use SIC technology, the wiring must be broken, and a SICinstalled between both ends.

In a similar manner, a communication network employing the electricalpower wiring of vehicles and vessel can be implemented, such as foraircraft, ships, trains, buses, automobiles, and so forth.

Implementing a Local Communication/Telephone System using SIC's

In this application, existing telephone wiring (either POTS or ISDN) isused as the electrically-conducting media for the local area network,and is used for both local area network data communication and fortelephony. The term “telephony” herein denotes any telephone ortelephonic communication, including both including voice (POTS) and data(ISDN). Telephone outlets are usually connected in point-to-pointtopology without a distribution point. To set up a network, each outletis replaced with SIC-based outlet. If there are distribution points,these distribution points must also be SIC equipped. This configurationresults in a high-performance LAN between the telephone outlets. Asidefrom sharing the same media, the local area network can be decoupledfrom the telephone system. Alternatively, the local area network and thetelephone system can be combined, such that telephony is digitallyintegrated into the local area network data.

The outside telephone service can be treated according to one of thefollowing alternatives:

1. No telephone support. In this configuration, the connection to thenetwork (usually to the public network) is cut, and the network is fullyinternal, with no external telephone service.

2. Telephone as Payload. In this configuration, the telephone capabilityis retained, and telephony data may be integrated into the datacommunication of the local area network. One of the SIC's (usually theone closest to a public telephone network interface) or other dedicatedmodule interconnects (via the communication interface for example) tothe network interface (NI). This unit emulates a telephone interface tothe NI, so that public network operation is transparent and continues toperform as normal. However, the signals associated with the telephoneinterface, either the voice itself and the control/signaling (onhook/off hook, ringing, etc.) are digitized and transmitted in thenetwork as data stream, as part of the communication taking place in thenetwork. In the SIC's interfaced to telephones, these signals areconverted back to analog (or in any original form) and thus can be usedwith standard telephones. In this case, telephone functionality is fullyretained. However, failure in the communication network may result inloss of the telephone service. This can be improved by means of a systemwhich disconnects the SIC's circuitry and restores the original wiringrouting (this can be easily implemented by relays, which bypass theSIC's upon failure detection, manual intervention, or other relevantoccasion).

3. Communication over POTS or ISDN. In this method, theelectrically-conducting media interconnecting SIC's is the telephonewiring of a building. This method involves the known mechanism ‘POTSSplitting’, currently used in conjunction with xDSL technologies. Thisrequires a filter which separates the low-frequency portion of thespectrum (usually carrying the POTS associated signals and power) fromthe high-frequency portion of the spectrum (used for communication). Insuch an application, the AC/DC units in the SIC are replaced with suchPOTS splitter modules. The low-frequency band (POTS related) is passedtransparently (similar to the power pass), and branched to the telephonejack. The high-frequency band is used for the communication between theSIC's. This combining of high-frequency local area network communicationon the same electrically-conducting media with low-frequency telephonydata is a form of frequency-domain multiplexing.

In the latter two alternatives, each in-wall telephone outlet isreplaced with a SIC based outlet having both a telephone jack and one(or more) communication jacks.

Computer Bus Extender

The SIC network can be used as a computer bus extender, such as an ‘ISAbus extender’, as illustrated in FIG. 10. In this configuration, a SIC1006 is equipped with a computer bus connector 1004 which is connected,for example, to one of the ISA bus slots in a computer 1002, totransport data between the local area network and computer 1002. AnotherSIC 1010, remotely located, also has a computer bus connector 1012, suchas an ISA bus extender. This allows for a transparent ISA buscapability, where the ISA bus data will be transported in bothdirections over electrically-conducting medium 1008. The ellipses ( . .. ) indicate that additional SIC's and electrically-conducting media maybe present in the local area network between SIC 1006 and SIC 1010.Shown as an example, a video frame grabber card 1014 is plugged intocomputer bus connector 1012, and a video camera 1016 is connected tovideo frame grabber card 1014. Normally, video frame grabber card 1014is plugged directly into an ISA bus slot, such as in computer 1002.Here, however, the local area network acts as a bus extender so thatvideo frame grabber 1014 and video camera 1016 can be located remotelyfrom computer 1002. The normal software driver for the ISA bus slot incomputer 1002 can used, since computer 1002 is unaware of the fact thatonly ISA emulation is taking place. This way, the capability of havinggeneral remote PC components and peripherals can be easily achieved.This configuration features the above-described advantages, and thismethod can be used to attain various goals, such as fault protection.Similarly, this method can be used to connect several units remotely toa computer, using different ports in the computer.

Implementing Multiplexers and PABX/PBX Functionality

A network of SIC's may be used to implement a multiplexer or a PABX/PBXfunctionality, as illustrated in FIG. 9. In this example, a SIC 900 isconnected to a high data rate connection, such as PCM bus 916, while SIC902 and SIC 906 are connected to telephones 908, 910, and 912. SIC 904functions as a repeater in this example.

In this example, the local area network functions as a multiplexer,wherein the bandwidth of the high data rate connection (PCM bus 916) ismultiplexed through SIC 900 to SIC 902 and SIC 906, each of which mayuse a different portion of the bandwidth of the high data rateconnection (PCM bus 916). Moreover, by the addition of telephones 908,910, and 912, the local area network of FIG. 9 functions as a voicemultiplexer.

Other Applications of the Invention

A number of applications of the present invention have been discussedabove. Additional applications include, but are not limited to:intercom, PABX/PBX, security systems, video surveillance, entertainmentbroadcasting services, time (clock) distribution, and audio/video signaldistribution. The networks implemented by the present invention canextend locally within a single building or over a neighborhood.

While the invention has been described with respect to a limited numberof embodiments and applications, it will be appreciated that manyvariations, modifications and other applications of the invention may bemade.

1. A device for coupling data signals and power to a plurality ofcables, for use with at least first, second and third point-to-pointcables each comprising at least one twisted wire pair and simultaneouslycarrying DC power and digital data signals, said device comprising: afirst connector for connecting to one end of said first cable; a firstmodem coupled to said first connector for full-duplex serial digitaldata communication over said first cable; a first transformer coupled topass only digital data signals between said first connector and saidfirst modem; a second connector for connecting to one end of said secondcable; a second modem coupled to said second connector for full-duplexserial digital data communication over said second cable; a secondtransformer coupled to pass only digital data signals between saidsecond connector and said second modem; a third connector for connectingto one end of said third cable; a third modem coupled to said thirdconnector for full-duplex digital data communication over said thirdcable; a power supply for providing DC power; and a single enclosurehousing said first, second and third connectors, said first, second andthird modems, said first and second transformers and said power supply,wherein: said third modem is coupled to said first modem for passingdigital data signals between said third and first cables; said thirdmodem is coupled to said second modem for passing digital data signalsbetween said third and second cables; said power supply is coupled tosaid first and second connectors for supplying DC power to said firstand second cables; and said device is addressable in a network.
 2. Thedevice according to claim 1, further comprising a power connectorconnectable to a power source for receiving power from the power source,the power connector being coupled to power at least said power supply.3. The device according to claim 1, wherein said device enclosure iswall mountable in a building.
 4. The device according to claim 1,wherein in said twisted wire pair of at least one of said first andsecond cables is connected to carry only DC power.
 5. The deviceaccording to claim 1, wherein DC power is carried over a respectivecable using distinct, dedicated wiring.
 6. The device according to claim1, wherein the DC power and data signals are carried over the same wirepairs in at least one of said cables.
 7. The device according to claim6, wherein the DC power and digital data signals are carried frequencymultiplexed over at least one of said cables.
 8. The device according toclaim 1, wherein said device has a manually assigned address
 9. Thedevice according to claim 1, wherein said device has an automaticallyassigned address.
 10. The device according to claim 1, wherein saiddevice has an address assigned by a unit communicating with the device.11. The device according to claim 1, wherein at least one of saidtransformers is a center tapped transformer.
 12. The device according toclaim 1, wherein said device is further connectable to one or more dataterminal equipments (DTE).
 13. The device according to claim 1, whereinat least one of the digital data signals includes a digitized telephonysignal.
 14. The device according to claim 13, wherein said device isconnectable to a telephone unit
 15. The device according to claim 1,wherein said device is further addressable in a Local Area Network(LAN).
 16. The device according to claim 1, wherein: at least one ofsaid modems is a Local Area Network (LAN) transceiver; at least one ofsaid connectors is a Local Area Network (LAN) connector; and at leastone cable is a LAN cable.
 17. The device according to claim 16, wherein:at least one of said modems is an Ethernet transceiver; and at least oneof said connectors is an Ethernet connector.
 18. The device according toclaim 1, wherein at least one of the cables is connected to performpacket-based digital data communication.
 19. The device according toclaim 1, wherein communication over said first cable is independent ofcommunication over said second cable.
 20. The device according to claim1, wherein: said device further functions as a multiplexer; and at leastone of said connectors is connected to a high data rate connection whosebandwidth is multiplexed to at least one other of said connectors. 21.The device according to claim 1, wherein: digital data carried over thethird cable comprises distinct first and second digital data streams;and said device is operative to pass only the first digital data streambetween said first and third cables and to pass only the second digitaldata stream between said second and third cables.
 22. The deviceaccording to claim 1, wherein: said device further functions as arepeater; and digital data received from a cable in one connector istransmitted to another cable via another connector.
 23. The deviceaccording to claim 1, further comprising: a first power coupler coupledto pass only DC power from said power supply to said first connector forcoupling DC power into said first cable; and a second power couplercoupled to pass only DC power from said power supply to said secondconnector for coupling DC power into said second cable.
 24. A system forcarrying DC power and digital data signals over multiple cables for usewith at least one equipment that is a source or destination of data,said system comprising: first, second and third devices, each of saiddevices containing at least one power consuming circuit; and first andsecond point-to-point cables in a building, each of said cablescomprising at least two conductors, said first cable being connected forcoupling said first and second devices to form a first digital databi-directional communication link and said second cable being connectedfor coupling said first and third devices to form a second digital databi-directional communication link; wherein: each of said first andsecond cables is connected to simultaneously carry both power and datasignals; each of said devices is either an equipment that is a source ordestination of data, or is connectable to an equipment that is a sourceor destination of data; at least a first one of said devices isconnectable to a power source for coupling the power source to saidfirst and second cables; and at least two of said devices are poweredonly by power carried over the respective cable connected to saiddevices.
 25. The system according to claim 24 wherein at least one ofsaid devices is wall mountable in a building.
 26. The system accordingto claim 24 wherein communication over said first communication linkdoes not preclude communication over said second communication link. 27.The system according to claim 24, wherein the same protocol is used onboth said first and second communication links.
 28. The system accordingto claim 24, wherein at least part of at least one of said first andsecond cables is in at least one wall of a building and is connected viaan outlet.
 29. The system according to claim 24, wherein the DC powerand digital data signals are carried in at least one of said cables overseparate wires.
 30. The system according to claim 24, wherein the DCpower and digital data signals are carried in at least one of saidcables over the same wires.
 31. The system according to claim 30,wherein the DC power and digital data signals are carried frequencymultiplexed over at least one of said cables.
 32. The system accordingto claim 24, wherein at least one of said devices is addressable in anetwork.
 33. The system according to claim 32, wherein said at least oneof said devices has a manually assigned address.
 34. The systemaccording to claim 32, wherein said at least one of said devices has anautomatically assigned address.
 35. The system according to claim 32,wherein said at least one of said devices has an address assigned by adata terminal equipment (DTE) communicating with said at least one ofsaid devices.
 36. The system according to claim 24, wherein at least oneof said communication links is connected to carry a digitized telephonysignal.
 37. The system according to claim 36, wherein at least one ofsaid devices is further a telephone unit or is connectable to atelephone unit.
 38. A device for coupling first, second and third cablesin a building, each cable comprising at least one twisted wire pair andbeing connected in a point-to-point configuration, and each cable beingconnected for carrying a respective one of first, second and thirdfull-duplex digital data signals, said device further being operativefor supplying power to at least one of the twisted wire pairs, saiddevice comprising: a first connector for connecting to the first cable;a first transceiver coupled to said first connector for full-duplexpacket-based point-to-point digital data communication over the firstcable; a second connector for connecting to the second cable; a secondtransceiver coupled to said second connector for full-duplexpacket-based point-to-point digital data communication over the secondcable; a third connector for connecting to the third cable; a thirdtransceiver coupled to said second connector for full-duplexpacket-based point-to-point digital data communication over the thirdcable; a DC power supply coupled to said first and second connectors forsupplying DC power to be carried over the first and second cables; and asingle enclosure housing said first, second and third connectors, saidfirst, second and third transceivers and said DC power supply, wherein:said first, second and third transceivers are coupled to pass digitaldata between said connectors for coupling digital data signals betweensaid cables; and said device is addressable in a network.
 39. The deviceaccording to claim 38, wherein the digital data signals carried over oneof the cables is independent of digital data signals carried over theother cables.
 40. The device according to claim 38, wherein: said deviceis further operative as a multiplexer; and at least one of saidconnectors is connected to a high data rate connection whose bandwidthis multiplexed to at least one other of said connectors.
 41. The deviceaccording to claim 38, wherein: the digital data signals carried overthe third cable comprises distinct first and second digital datastreams; and said device is operative to pass only the first digitaldata stream between the first and third cables and to pass only thesecond digital data stream between the second and third cables.
 42. Thedevice according to claim 38, wherein: said device is further operativeas a repeater; and digital data signals received from a cable at oneconnector is transmitted to another cable via another connector.
 43. Thedevice according to claim 38, wherein said device has a manuallyassigned address.
 44. The device according to claim 38, wherein saiddevice has an automatically assigned address.
 45. The device accordingto claim 38, wherein said device has an address that is assigned by aunit coupled to said device through a local area network.
 46. The deviceaccording to claim 38, wherein: the cables are local area networkcables; and said connectors are local area network connectors.
 47. Thedevice according to claim 38, wherein: said connectors are Ethernetconnectors; and said transceivers are Ethernet transceivers.
 48. Thedevice according to claim 38, wherein said device is constructed to haveat least one of the following: a form substantially similar to that of astandard outlet; wall mounting elements substantially similar to thoseof a standard wall outlet; a shape allowing direct mounting in an outletopening or cavity; and a form to at least in part substitute for astandard outlet.
 49. The device according to claim 38, wherein saiddevice is wall-mountable in a building.
 50. The device according toclaim 38, wherein said device is mountable into an outlet cavity. 51.The device according to claim 38, further comprising a fourth connectorfor receiving a power signal, and wherein said DC power supply isconnected to be powered by the power signal.
 52. The device according toclaim 51, wherein: said fourth connector is connectable to receive an ACpower signal; and said power supply is an AC/DC power supply.
 53. Thedevice according to claim 38, wherein the DC power is carried over atleast one of the cables using one or more dedicated twisted wire pairsseparated from one or more other twisted wire pairs carrying a fullduplex digital data signal.
 54. The device according to claim 38,wherein DC power and full duplex data signals are carried together overthe same wires.
 55. The device according to claim 54, further comprisingone or more transformers coupled for passing only digital data signalsbetween one of said connectors connected to a cable carrying DC powerand the respective transceiver coupled to said one of said connectors.56. The device according to claim 38, further comprising firmware and aprocessor executing said firmware, said processor being coupled tocontrol all said modems.
 57. The device according to claim 38, furthercomprising a current limiter coupled between said DC power supply andsaid first connector for limiting DC current flow into the first cable.58. The device according to claim 57 wherein said current limiter is afuse.
 59. The device according to claim 57, wherein said device isfurther operative to measure the DC current supplied to the first cable.60. The device according to claim 38 further comprising: a firstpower/data splitter/combiner coupled between said first connector, saidfirst modem and said DC power supply for passing data only between saidfirst transceiver and said first connector, and for passing power onlybetween said DC power supply and said first connector; and a secondpower/data splitter/combiner coupled between said second connector, saidsecond transceiver and said DC power supply for passing data onlybetween said second modem and said second connector, and for passingpower only between said DC power supply and said second connector. 61.The device according to claim 38, wherein said device is furtheroperative for on/off control of the DC power from said DC power supplyto said first connector.
 62. The device according to claim 61, whereinthe power control effected by said device is responsive to a digitaldata signal.
 63. A network for coupling digital data signals and DCpower, the system comprising: first, second and third devices, eachenclosed in a single enclosure and addressable in the network; and firstand second cables in a building, each of said cables comprising at leastone twisted wire pair, each of said cables being connected in apoint-to-point configuration, and each of said cables being connected toconcurrently carry digital data signals and DC power, wherein: saidfirst and second devices are connected by said first cable forfull-duplex, packet-based digital data communication between said firstand second devices; said first and third devices are connected by saidsecond cable for full-duplex, packet-based digital data communicationbetween said first and third devices; the first device further transmitsDC power to said first and second cables; said second device is onlypowered by DC power carried over said first cable; and said third deviceis only powered by DC power carried over said second cable.
 64. Thenetwork according to claim 63, wherein digital data signals carried oversaid first cable are independent of digital data signals carried oversaid second cable.
 65. The network according to claim 63, wherein: saidnetwork is further operative as a multiplexer; and at said first deviceis connected to a high data rate connection whose bandwidth ismultiplexed to at least one of said cables.
 66. The network according toclaim 63, wherein said network is further operative as a repeater; anddigital data signals received from one of said cables is transmitted tothe another one of said cables.
 67. The network according to claim 63,wherein at least one of said devices has a manually assigned address.68. The network according to claim 63, wherein at least one of saiddevices has an automatically assigned address.
 69. The network accordingto claim 63, wherein at least one of said devices has an addressassigned by a unit coupled to said at least one of said devices througha local area network.
 70. The network according to claim 63, whereinsaid cables are local area network cables and are connected using localarea network connectors.
 71. The network according to claim 63, whereinthe digital data communication is Ethernet based.
 72. The networkaccording to claim 63, wherein at least one of said devices is furtherconstructed to have at least one of the following: a form substantiallysimilar to that of a standard outlet; wall mounting elementssubstantially similar to those of a standard wall outlet; a shapeallowing direct mounting in an outlet opening or cavity; and a form toat least in part substitute for a standard outlet.
 73. The networkaccording to claim 63, wherein at least one of said devices iswall-mountable in a building.
 74. The network according to claim 63,wherein at least one of said devices is mountable into an outlet cavity.75. The network according to claim 63, wherein each of said cablescomprises at least one first twisted wire pair connected for carrying DCpower and at least one second twisted wire pair, separate from saidfirst twisted wire pair, connected for carrying full duplex digital datasignals.
 76. The network according to claim 63, wherein said cables areconnected for carrying DC power full duplex data signals together overthe same wires.
 77. The network according to claim 63, furthercomprising a current limiter for limiting the DC current flowing intosaid first cable.
 78. The network according to claim 77, wherein saidcurrent limiter is a fuse.
 79. An apparatus for time domainmultiplexing/de-multiplexing between a high data rate connection andmultiple low data rate connections, for use with point-to-point localarea network wiring segments in a building, each segment comprising atleast one twisted wire pair and being connected to carry full duplexdigital data signals, said apparatus comprising: a plurality of low datarate connectors, each for connecting to a distinct point-to-point localarea network wiring segment; a plurality of low data rate transceivers,each coupled to a respective one of said low data rate connectors, fortransmitting and receiving full-duplex serial digital data signals withthe respective point-to-point local area network wiring segment; a highdata rate connector for connecting to one of the point-to-point localarea network wiring segments; and a high data rate transceiver coupledto said high data rate connector for transmitting and receivingfull-duplex serial digital data signals with the one of thepoint-to-point local area network wiring segments, wherein: saidapparatus operative as a time-domain demultiplexer and as a time-domainmultiplexer; digital data signals received from said high data rateconnector are divided into multiple distinct streams and each distinctstream is transmitted into one of said plurality of low data rateconnectors, digital data signals received from said plurality of lowdata rate connectors are combined into a single data stream transmittedto said high data rate connector; and said apparatus is addressable in alocal area network.
 80. The apparatus according to claim 79, whereinsaid apparatus has a manually assigned address.
 81. The apparatusaccording to claim 79, wherein said apparatus has an automaticallyassigned address.
 82. The apparatus according to claim 79, wherein saidapparatus has an address that is assigned by a data unit coupled to saidapparatus through a local area network.
 83. The apparatus according toclaim 79, wherein each one of said high data rate and low data ratetransceivers is operative for point-to-point communication only with asingle mating transceiver of substantially the same type.
 84. Theapparatus according to claim 79, wherein each one of said high data rateand low data rate transceivers is a local area network transceiver. 85.The apparatus according to claim 84, wherein each one of said high datarate and low data rate transceivers is an Ethernet transceiver and eachone of said low data rate and high data rate connectors is an Ethernetconnector.
 86. The apparatus according to claim 79, further comprising asingle enclosure housing said transceivers and connectors, wherein saidsingle enclosure is constructed to have at least one of the following: aform substantially similar to that of a standard outlet; wall mountingelements substantially similar to those of a standard wall outlet; ashape allowing direct mounting in an outlet opening or cavity; and aform to at least in part substitute for a standard outlet.
 87. Theapparatus according to claim 79 further comprising a single enclosurehousing said transceivers and connectors, wherein said single enclosureis wall mountable in a building.
 88. The apparatus according to claim79, further comprising a single enclosure housing said transceivers andconnectors, wherein said single enclosure is mountable into an outletcavity.
 89. The apparatus according to claim 79, wherein at least one ofthe point-to-point local area network wiring segments is connected toconcurrently carry DC power together with the full-duplex digital datasignals, and said apparatus further comprises: an AC power connector forconnecting to powerline wiring to receive AC power therefrom; and anAC/DC power supply connected to said AC power connector to be power fedby the AC power and to supply DC power, wherein the AC/DC power supplyis coupled to at least one of said connectors for feeding DC power ontothe wiring.
 90. The apparatus according to claims 89, wherein one ormore dedicated twisted wire pairs of at least one of the segments areconnected for carrying the DC power, which dedicated twisted wire pairsare separated from one or more other twisted wire pairs connected forcarrying a full duplex digital data signal.
 91. The apparatus accordingto claim 89, wherein the DC power and a full duplex data signal arecarried together over the same twisted wire pairs of at least one of thesegments.
 92. The apparatus according to claim 89, further comprising acurrent limiter coupled between said AC/DC power supply and a connectorfor limiting DC current flowing into the wiring segment connected tosaid at least one connector.
 93. The apparatus according to claim 92,wherein said current limiter is a fuse.
 94. The apparatus according toclaim 89, wherein said apparatus is further operative to measure DCcurrent supplied to one of the wiring segments.
 95. The apparatusaccording to claim 79, wherein at least one of the point-to-point localarea network wiring segments is connected to concurrently carry first DCpower together with a full-duplex digital data signal, and saidapparatus further comprises: a DC/DC power supply coupled to one of saidconnectors to be power fed from the first DC power carried over thewiring segment and to supply second DC power, wherein said DC/DC powersupply is coupled to at least one of said transceivers for feeding thetransceiver by the second DC power.
 96. The apparatus according toclaims 95, wherein one or more dedicated twisted wire pairs of at leastone of the segments are connected for carrying the first DC power, whichdedicated twisted wire pairs are separated from one or more othertwisted wire pairs connected for carrying the full duplex digital datasignal.
 97. The apparatus according to claim 95, wherein the DC powerand the full duplex data signal are carried together over the sametwisted wire pairs of at least one of the segments.
 98. The apparatusaccording to claim 79, further comprising one or more transformerscoupled for passing only a digital data signal between a connectorconnected to a wiring segment that is also connected to carry DC powerand a respective transceiver.
 99. The apparatus according to claim 79,further comprising firmware and a processor for executing said firmware,said processor being coupled to control all of said transceivers.
 100. Adevice for configuring a local area network in a building for thetransport of power and data signals across a wiring, wherein the wiringincludes at least first and second wiring segments, said devicecomprising: first and second ports each connected to a respective one ofthe first and second wiring segments; first and second data couplerseach coupled to a respective one of said first and second ports, andeach having a data signal port operative to pass only a data signal;first and second modems each coupled to said data signal port of arespective one of said first and second data couplers, for full duplexdata signal communication with a respective one of said first and secondwiring segments; at least one data interface connector coupled to atleast one of said modems and operative for establishing a data signalconnection with a data terminal equipment unit; first and second powercouplers each coupled to a respective one of said first and secondports, and each having a respective one of first and second power signalports, each power signal port being operative to pass only a powersignal; a power supply coupled to the first power signal port and to atleast one of said modems to be powered by the power signal and forpowering said first modem; and means for allowing the communication of adata signal over the first wiring segment to be independent of thecommunication of a data signal over the second wiring segment, whereinthe second power signal port is coupled to the first power signal port.101. The device according to claim 100, further comprising a powerconnector connectable to a power source for receiving power from thepower source, the power connector being coupled to pass at least onepower signal.
 102. The device according to claim 100, further comprisingmeans for mounting said device on a wall.
 103. The device according toclaim 100, wherein said device is mountable in an outlet.
 104. Thedevice according to claim 103, wherein the outlet is one of a telephoneoutlet and a power outlet.
 105. The device according to claim 100,wherein at least one of the power signals is a direct current signal.106. The device according to claim 100, wherein at least one of thepower signals is an alternating current signal.
 107. The deviceaccording to claim 100, wherein at least one of the power signals iscarried over a respective wiring segment using distinct/dedicatedwiring.
 108. The device according to claim 100, wherein power and datasignals are carried frequency multiplexed over at least one of thewiring segments, and at least one of said couplers further comprises afilter.
 109. The device according to claim 100, wherein said device isaddressable.
 110. The device according to claim 109, wherein said devicehas a manually assigned address.
 111. The device according to claim 109,wherein said device has an automatically assigned address.
 112. Thedevice according to claim 109, wherein said device has an addressassigned by a data terminal equipment unit connected to said device.113. The device according to claim 100, wherein at least one of saidcouplers comprises a center tap transformer.
 114. The device accordingto claim 100, further comprising an enclosure housing at least part ofsaid device within a data terminal equipment unit.
 115. The deviceaccording to claim 100, wherein at least one of the data signalsincludes a digitized telephony signal.
 116. The device according toclaim 100, wherein said device is connectable to a telephone unit. 117.The device according to claim 100, further comprising a power connectorconnectable to a power source for receiving power from the power source,said power connector being coupled to at least one power signal.
 118. Anetwork for carrying data and power signals, said network comprising:first, second and third nodes, each of said nodes containing at leastone power consuming circuit; and first and second wiring segments in abuilding, each of said segments comprising at least two conductors, saidfirst wiring segment coupling said first and second nodes to form afirst bi-directional communication link and said second wiring segmentcoupling said first and third nodes to form a second bi-directionalcommunication link, wherein: at least one of said wiring segments isconnected for simultaneously carrying both data and power signals; saidfirst communication link is connected to carry data independent of datacarried by said second communication link; each of said nodes isconnectable to a data terminal equipment unit for coupling the dataterminal equipment unit to at least one of said communication links; atleast a first one of said nodes is connectable to a power source forcoupling the power source to at least one power signal over one of saidwiring segments connected to said first node; and at least said secondnode is powered by a power signal carried over said first wiring segmentconnected to said second node.
 119. The network according to claim 118,wherein at least one of the nodes is included in an outlet.
 120. Thenetwork according to claim 119, wherein at least one of the nodes isincluded in one of a telephone outlet and a power outlet.
 121. Thenetwork according to claim 118, wherein at least one of said wiringsegments is composed of wiring previously installed in the building.122. The network according to claim 118, wherein at least one of thewiring segments is one of: telephone wiring; and power wiring.
 123. Thenetwork according to claim 118, wherein the power signal is carried overat least one of said wiring segments using distinct/dedicated wiring.124. The network according to claim 118, wherein the power and datasignals are carried frequency multiplexed over at least one of saidwiring segments.
 125. The network according to claim 118, wherein atleast one of said nodes is addressable.
 126. The network according toclaim 125, wherein said at least one of said nodes has a manuallyassigned address.
 127. The network according to claim 125, wherein saidat least one of said nodes has an automatically assigned address. 128.The network according to claim 125, wherein said at least one of saidnodes has an address assigned by a data terminal equipment unitconnected to said at least one of said nodes.
 129. The network accordingto claim 118, further comprising an enclosure of a data terminalequipment unit housing at least one of said nodes.
 130. The networkaccording to claim 118, wherein at least one of said communication linksis connected to carry a digitized telephony signal.
 131. The networkaccording to claim 118, wherein at least one of said nodes is furtherconnectable to a telephone unit.
 132. The network according to claim118, further comprising a power connector coupled to receive a powersignal carried by said network for powering said at least one powerconsuming circuit contained in one of said nodes.
 133. The networkaccording to claim 118, wherein the power signal.